Drill Assembly

ABSTRACT

Drill assembly for making a hole into a soil or rock which arrangement comprises a pilot bit ( 10 ) drilling the middle part of the hole and a ring bit ( 1 ) drilling the outer circle of the hole in which case in the drilling situation the ring bit ( 1 ) is adjusted around the pilot bit ( 10 ) and rotary movement and drilling impacts are directed from the pilot bit ( 10 ) to the ring bit ( 1 ) with the help of the mentioned surfaces ( 4 - 6 );( 7 - 9 ),( 15, 16 ) adjusted between the bits and conveying power and that the ring bit ( 1 ) can be removed around the pilot bit ( 10 ) and can be installed to it and that further a coupling ring ( 2 ) belongs around the ring bit ( 1 ) in order to join a casing pipe, which can be pulled to the drilled hole, to the ring bit ( 1 ) with the help of the mentioned coupling ring. The coupling ring. ( 2 ) is adjusted around the periphery of the ring bit ( 1 ) in such a way that of the parts ( 13 ) taking part in the locking of the coupling ring ( 2 ) at least two are located at the different sides of the line (L) when the arrangement is assembled which line runs essentially through the middle point of the surface ( 5 ) conveying the rotation of the ring bit ( 1 ).

Invention relates to a drill assembly for making a hole into a soil orrock which assembly comprises a pilot bit drilling the middle part ofthe hole and a ring bit drilling the outer circle of the hole in whichcase in the drilling situation the ring bit is adjusted around the pilotbit and rotary movement and drilling impacts are directed from the pilotbit to the ring bit with the help of the mentioned surfaces adjustedbetween the bits and conveying the impacts and that the ring bit can beremoved around the pilot bit and can be installed to it and that furthera coupling ring which can be locked to the ring bit belongs around thering bit in order to join a casing pipe, which is to be pulled into thedrilled hole, to the ring bit through the mentioned coupling ring.

A drill assembly according to the above mentioned preamble is previouslyknown for example from the publication WO 2004/057148 in which the shownring bit is relatively long in the axial direction because the upperpart of the ring bit comprises first a flange part comprising spikesmade of for example hard metal. After the flange part there is a acasing part to which a groove has first been formed and after thatlocking hole formations with the help of which the ring bit is locked tothe pilot bit. Also a cutter shoe is relatively long in the axialdirection when the cutter shoe is adjusted to exceed essentially in theaxial direction both the groove and the locking hole forms located atthe casing part of the ring bit. Also the body of the pilot bit is longin the axial direction and the length required by the counter formsadjusted to the locking hole forms of the ring bit is only a small partof it, less than a quarter.

With the drill assembly according to the invention significantimprovements can be achieved to the existing prior art according to thepublication WO 2004/057148 when as a result of the invention as shortring bit as possible can be constructed. It is characteristic of theinvention that the coupling ring is adjusted around the periphery of thering bit in such a way that of the parts taking part in the reciprocallocking of the coupling ring and the ring bit at least two are locatedat different sides of the line L when the arrangement is assembled whichline runs essentially through the middle point of the surface conveyingthe rotation of the ring bit.

The advantage of the invention is the fact that the size of the ring bitbecomes essentially shorter in the axial direction thanks to the newlocating and installation way of the coupling ring. Similarly the lengthneeded for the coupling ring becomes shorter. The thickness of thecylinder part of the ring bit must however be of a certain size due tohard metal installations in which case the thickness of the cylinderpart allows the formation of grooves at the outer surface of the ringbit for the attachment of the coupling ring. In some cases even onegroove is enough for the coupling ring but two or even several groovesstill do not increase too much the length of the coupling ring. Thecoupling ring is installed most advantageously by shrinking or weldingon top of the ring bit. In addition to that the flushing groove becomesshorter when the ring bit becomes shorter in which case the throttlingcaused by the flushing stream and occurring in the pneumatic line of thedrilling diminishes and the drilling speed increases. When the partstaking part in the locking of the coupling ring, for example shoulderrings, are located in the way according to the invention in relation tothe hole forms of the ring bit, enough unbroken groove length stays atthe ring bit as counter surfaces for the shoulder rings of the couplingring in spite of the hole forms of the ring bit.

In the following the invention is described more detailed by referringto the accompanying drawings in which

FIG. 1 shows a ring bit according to the invention and a coupling ringas a cut view.

FIG. 2 shows the position of a coupling ring in relation to the ringbit.

FIG. 3 shows a pilot bit as a side view.

FIG. 4 shows the grooves of a bayonet locking formed to the ring bit.

In the FIG. 1 there is a ring bit 1 which has a cylindrical body. Thefront part of the body comprises a flange part 14 forming an extensionwhich flange part has a length h2 in the axial direction and to whichflange part hard metal spikes 13 are attached. The cylinder partdirected in the back from the flange part 14 comprises two grooves 12 atits outer surface to which grooves a coupling ring 2 is attached in sucha way that ring overhangs 13 of the inner surface of the coupling ringare located into the mentioned grooves 12. The cylinder part of the ringbit 1 also has hole forms in order to lock it to the counter forms ofthe pilot bit in such a known way. The hole forms comprise surfacesconveying impacts in the axial direction, such as surfaces 4 and 6 andsurfaces 5 conveying rotation.

The surface 4 has lift, especially a surface with a constant lift. Thiscylinder part located behind the flange part 14 of the ring bit 1comprises essentially only counter forms 12 for the ring overhangs ofthe coupling ring 2 and counter forms 4-6; 5; 16; 17 of the lockingforms 7-9 of the pilot bit 10.

The above mentioned hole forms 4 - 6 are located at the same place atthe cylinder part of the ring bit 1 as the coupling ring 2. The couplingring 2 has a length hl in the axial direction. The hole forms 4-6require length from the cylinder part essentially the same amount thanthe coupling ring 2 does. The ring bit 1 will thus have a shortconstruction in the axial direction. The hole forms 4-6 go through thecylinder part of the ring bit. Due to this the grooves 12 in the ringbit are not necessarily continuous grooves around the cylinder part.

In the FIG. 3 a pilot bit 10 is shown which has locking hole forms 7-9in a such known way as a counter form to the hole forms of the ring bit1. One has been able to shorten the length of the cross-die head of thepilot bit 10 compared to the previous cross-die heads by using the ringbit and the coupling ring according to the invention.

In the FIG. 4 a hole form for the bayonet locking is shown in the ringbit. There is a vertical groove 18 at the inner surface of the ring bit1 and at the end of it there is a horizontal part 17. A protrudingpiece, for example quadrangular, located at the side of the pilot bitmoves in this solution first to the end of a vertical groove 18 in asuch known way and with a reversion of the pilot bit moves against thesurface 5 located at the end of a horizontal groove 17 and functions asthe part which conveys the rotation of the pilot bit to the ring bit.Also this piece can convey impacts to the ring bit in its lockingposition by conveying impacts onto the surface 16 of the ring bit 1. Inthis case the depths of the grooves 17 and 18 are less than the wallthickness of the ring bit 1.

1. Drill assembly for making a hole into a soil or rock which assemblycomprises a pilot bit (10) drilling the middle part of the hole and aring bit (1) drilling the outer circle of the hole in which case in thedrilling situation the ring bit (1) is adjusted around the pilot bit(10) and rotary movement and drilling impacts are directed from thepilot bit (10) to the ring bit (1) with the help of the mentionedsurfaces (4-6);(7-9);(15, 16) adjusted between the bits and conveyingpower and that the ring bit (1) can be removed around the pilot bit (10)and can be installed to it and that further a coupling ring (2), whichcan be locked to the ring bit (1), belongs around the ring bit (1) inorder to join a casing pipe, which can be pulled into the drilled hole,to the ring bit (1) with the help of the mentioned coupling ring,characterized in that the coupling ring (2) is adjusted around theperiphery of the ring bit (1) in such a way that of the parts (13)taking part in the reciprocal locking of the coupling ring (2) and thering bit (1) at least two are located at different sides of the line (L)when the arrangement is assembled which line runs essentially throughthe middle point of the surface (5) conveying the rotation of the ringbit (1).
 2. Drill assembly according to the claim 1, characterized inthat the ring bit (1) comprises at least two annular grooves (12) at theouter circle in which annular grooves the parts taking part in thelocking, like shoulder rings (13), and which are located at the innersurface of the coupling ring (2) are adjusted to rotate and move in alimited way in the axial direction of the drill.
 3. Drill assemblyaccording to the claim 1, characterized in that the back part (peripherypart) of the flange part (14) of the ring bit (1) comprises essentiallyonly the counter forms (12) of the locking forms (13) of the couplingring (2) and the counter forms (4 6); (5, 16, 17) of the locking forms(7-9) of the pilot bit (10).
 4. Drill assembly according to the claim 1,characterized in that the surfaces (4-6);(7-9); (5, 16) of the bits (1);(10) sometimes conveying force and impacts are essentially at that partof the cylinder part of the ring bit (1) which begins from the flangepart (14) and ends to the trail edge of the ring bit (1).
 5. Drillassembly according to the claim 1, characterized in that the innersurface of the ring bit (1) is even without the forms which diverge fromit towards the pilot bit (10).
 6. Drill assembly according to the claim1, characterized in that the counter parts (4-6) of the locking forms(7-9) formed to the pilot bit (10) and located at the periphery part ofthe ring bit (1) are forms which are directed through the periphery partof the ring bit (1).
 7. Drill assembly according to the claim 1,characterized in that the counter forms (5, 16, 17) of the locking formsformed to the pilot bit (10) and located at the periphery part of thering bit (1) are surfaces and grooves formed to the periphery part ofthe ring bit (1), to its inner surface which surfaces and grooves do notpenetrate the wall of the periphery part.
 8. Drill assembly according tothe claim 1, characterized in that the surface located at the peripherypart of the ring bit (1) and receiving impacts from the pilot bit (10)is a surface with a lift (4).